title: Evaluation of exhaled breath condensate pH as a biomarker for COPD.
abstract: BACKGROUND
  We assessed the utility of EBC pH as a biomarker in COPD in a large cohort of well-characterised individuals with COPD and control subjects from the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE) study. We also determined short term reproducibility and the response of EBC to oral prednisolone.
  
  
  METHODS
  EBC was collected with R-Tubes(TM), using techniques for sampling and measurement that have been shown to be reproducible.
  
  
  RESULTS
  EBC pH was lower in COPD (n = 676, 7.29 ± SD 0.60) and in smoking controls (n = 31, 7.18 ± 0.85), compared with non-smoking controls (n = 50, 7.59 ± 0.44, p = 0.0008 and 0.0033 respectively), but was not different between COPD and smoking controls. There was no relationship between EBC pH and disease severity, as assessed by the percent predicted FEV(1), nor with airway inflammation as assessed by sputum leukocyte counts. Treatment with 20 mg.day-1 prednisolone for 4 weeks did not change EBC pH.
  
  
  CONCLUSIONS
  EBC pH is lower in COPD than in healthy control non-smokers, but does not differentiate COPD from smokers without COPD, relate to disease severity or to airway inflammation, and does not respond to corticosteroids. EBC pH therefore does not appear to be a useful biomarker in COPD.
authors.affiliation: ELEGI Colt Research Labs, MRC Centre for Inflammation Research, The Queen's Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, Scotland, UK. w.macnee@ed.ac.uk
authors.forename: William
authors.initials: W
authors.lastname: MacNee
authors.forename: Stephen I
authors.initials: SI
authors.lastname: Rennard
authors.forename: John F
authors.initials: JF
authors.lastname: Hunt
authors.forename: Lisa D
authors.initials: LD
authors.lastname: Edwards
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Miller
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: Locantore
authors.forename: Ruth
authors.initials: R
authors.lastname: Tal-Singer
mesh_terms: D000305:Adrenal Cortex Hormones / Q000494:pharmacology; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D001944:Breath Tests; D003937:Diagnosis, Differential; D045853:Exhalation; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D018375:Neutrophil Activation / Q000502:physiology*; D011239:Prednisolone / Q000494:pharmacology; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000378:metabolism; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D012907:Smoking / Q000378:metabolism; D013183:Sputum / Q000166:cytology
chemical_list: D000305:Adrenal Cortex Hormones; D015415:Biomarkers; D011239:Prednisolone